At work, Clark Griswold (Chevy Chase) has invented a long life food preservative, earning him a large bonus check. Clark announces to his family that he is taking them on vacation. Enthusiasm wanes, however, when Clark says they are headed to Las Vegas, Nevada. His wife, Ellen (Beverly D'Angelo), and teenage daughter, Audrey (Marisol Nichols) have their doubts, as Las Vegas is not known for its family-friendly atmosphere, while teenage son Rusty (Ethan Embry) appears to be more eager. Will everything go smoothly? Don't bet the house.